This invention is directed to a process for producing refined sugar from raw juices and an apparatus useful in such process to separate undissolved impurities from such juices.
The manufacture of refined sugar for human consumption begins with the treatment of dark colored juices which are extracted from plants. The raw juice may contain gums, waxes, proteins, organic acids, minerals, vegetable particles, sand, dirt, and other suspended solids. This manufacturing process primarily utilized in the prior art occurs in two main steps: (1) production of raw sugar, and (2) refinement of the raw sugar.
Meade and Chen, in their Cane Sugar Handbook, Eleventh Edition (John Wiley & Sons, 1985), disclose a process for the manufacturing of the raw sugar in which, after the extraction of the juice from the sugar cane or beet, hot or cold juices are treated with the addition of lime (calcium hydroxide). The line reacts with the organic acids in the juice when it is heated, by which flocculation insoluble flocs are formed. These are separated in a tray clarifier or multicell or some other device used in a "boiling house". Gravity forces the flocs with the most suspended solids to settle in the bottom of the tray while the clear juice is collected in the top of the tray. The juice is then evaporated in a multi effect system to 60.degree.-62.degree. Brix, and the concentrated syrup is then crystallized in a sugar pan. The crystals of raw sugar are then separated from the mother liquor by centrifugation. In many instances, the raw sugar crystals have impurities included inside the crystal.
The raw sugar is refined by washing the crystals with hot water to remove the film of syrup over the crystal. While more water gives better results, too much water can dissolve the sugar and decrease the yield of sugar. The sugar then is melted to begin the treatment. Most of the raw sugar refineries use phosphatation to remove parts of the impurities in the solution and also to remove some of the color bodies. Phosphoric acid and lime are added to the solution which is then heated in a clarifier, creating formation of insoluble flocs. Separation occurs when an air is pumped through the clarifier to rise the flocs to the surface of the solution. The clear liquor is then filtered to remove the remaining solids, and the scum is desweetened, to recover the sugar. Following this, the liquor is decolorized by contact with bone char, granular activated carbon or other absorbents, and, in some instances, ion exchange resins. When carbon beds are used, the carbon may lose its absorbent power and must be reactivated in a furnace. Ion exchange resins may be regenerated inside the chamber. After decolorization, the liquor is crystallized in a sugar pan, and sugar is separated from the mother liquor by centrifugation and is washed. The sugar is then dried in a continuous dryer and packed according to market needs.
There has been a long felt need in the industry to simplify the production of refined sugar and improve efficiency, but, to date, no such process has been developed which would be commercially viable. Given the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide an improved process for refining sugar from raw juices which is simpler and more efficient than those in the prior art.
It is another object of the present invention to provide a process for refining sugar from raw juices which avoids the intermediate production and handling of raw sugar.
It is a further object of the present invention to provide a process for refining sugar from raw juices which utilizes methods and apparatus to reduce the time of production, including the time for removing undissolved impurities in sugar juices.